The Colorado River Delta captured in a 2004 image from the International Space Station. Via NASA Earth Observatory.

Monitoring report documents renewed life

Staff Report

In just two years following a man-made flood in the Colorado River Delta, cottonwoods and willows have grown 10 feet tall, rebuilding habitat for other native plants and animals, according to a new monitoring report on the international experiment to re-water the long-arched region.

While most recent research suggests that the Colorado River will be depleted well beyond current demands as global temperatures increase, there may be one small bright spot on the horizon. Even if runoff from snow declines, groundwater replenishment in the basin may hold stead under projected increases in precipitation, the U.S. Geological Survey and U.S. Bureau of Reclamation found in a new study.

“You can’t manage what you don’t measure,” said Fred Tillman, lead author and USGS scientist. “These results are the first step in understanding the quantity of groundwater we can expect in the Upper Colorado River Basin; however, further studies are needed to help more accurately forecast future groundwater availability.”

The Colorado River is a critically important source of water for more than 35 million people in the United States and 3 million people in Mexico. As much as half the water flowing in the rivers and streams in the Upper Colorado River Basin originates as groundwater. Understanding how much groundwater is available and how it’s replenished is important to sustainably manage both groundwater and surface water supplies in the Colorado River basin now and in the future.

In the new study, USGS and Reclamation scientists estimated projected changes in groundwater recharge for the Upper Colorado River Basin from recent historical (1950–2015) through future (2016–2099) time periods using climate projections and a groundwater-recharge model.

Simulated future groundwater recharge through 2099 is generally expected to be somewhat greater than the historical average in most decades due to an anticipated wetter future climate in the basin under the most advanced climate modeling projections. Groundwater resources are replenished through increases in precipitation, which may offset reductions from increased temperatures. The full report is available online in the journal Geophysical Research Letters.

But researchers urged caution interpreting the results because a few of the models suggested decreased future recharge relative to the historical climate period.

Human management of natural ecosystems always has unintended consequences, and the Colorado River is no exception. After decades of intense dam building and diversions, the mighty river is a mere shadow of it former self, reduced to a trickle in some places and polluted by return flows in others. Along its entire length, ecosystems, including riparian zones and native fish, have suffered, with some of the biggest impacts in the Colorado River delta.

In an effort to restore at least some key reaches of the river, scientists and water managers have teamed up to try mimic some of the Colorado’s natural functions, with controlled releases of water to build up beaches. Those efforts culminated in early 2014 during an eight-week experiment that unleashed a mighty torrent of water from Morelos dam (on the border with Mexico and the USA).

The huge surge (130 million cubic metres) of water raised river levels down to the delta, which has been starved of water for decades. Scientists closely monitored how the release — and potential future releases — affect agricultural crops and natural plant and animal life of the lower delta.

Groundwater is a huge factor in assessing climate change impacts on the Colorado River. @bberwyn photo.Resource managers need as much information as possible about Colorado River flows to make sustainable management decisions.

Staff Report

Resource managers grappling with the vexing question of how to allocate Colorado River water to the thirsty cities, ranches and farms of the Southwest have some new food for thought. A new U.S. Geological Survey study published this week in the journal Water Resources Research shows that more than half the streamflow in Upper Colorado River Basin originates as groundwater.

April storms boosted Colorado’s snowpack, with near average runoff and river flows expected during the spring and summer in most parts of the state.Southern parts of Colorado have not had above average snowpack readings for several years in a row, which could be part of the “new normal” in the global warming era

Staff Report

April storms helped boost Colorado’s statewide snowpack to above average, but two river basins in the southern part of the state continue to report below normal readings.

The state’s mountain areas benefited the most from a series of wet, El Niño-fueled storms, bringing precipitation for the water year to average, according to Brian Domonkos, the Colorado snow survey supervisor for the USDA Natural Resources conservation service.

“At this time last year the water supply outlook was grim at best,” Domonkos said. “Colorado’s current snowpack and precipitation levels are right where we want to be this time of year. Elsewhere in the Western United States seasonal snowpack during 2016 succumbed to early spring warming and did not recover as Colorado did from recent storms,” he added. Continue reading “April storms boost Colorado snowpack”→

A new gray water program in Denver could help temper demand for new water development projects in Colorado. @bberwyn photo.

City takes big step toward more sustainable water use

Staff Report

Denver, Colorado took a big step toward meeting an ambitious 20 percent water conservation target by passing an ordinance authorizing the use of gray water for residential, commercial and industrial purposes. The city hopes to cut per capita use of potable water by 20 percent by 2020.

Enabling large water users like hotels, multi-family residential complexes and dormitories, as well as industrial facilities, to use gray water will not only help conserve a valuable resource, it will help those facilities save money. Continue reading “Denver authorizes gray water program”→

Forests may grow faster but will produce less water as global temperatures warm. @bberwyn photo.

Staff Report

After taking a big-picture look at the water cycle, U.S. Forest Service researchers say global warming may decrease the amount of water produced by forests and grasslands across the country — even with increases in precipitation.